The subject invention is directed to the art of vascular catheters and, in particular, to the guidance of catheters using a low friction resilient control wire during introduction of catheters in such techniques as angiography and arteriography.
In certain diagnostic techniques, it is necessary to insert a catheter through the blood vessels to a particular destination, and this frequently makes it necessary to guide the catheter into one of several alternate channels, as into a branching vessel. Vascular catheters have heretofore been commonly formed with a curved but flexible distal tip portion which may be used to guide the cannula by twisting it from side to side during insertion to select the desired one of several vessels. Attempts have been made to control the curvature of the distal tip alone so that it may be directed forward or to the side as desired during its insertion. This technique has meet with little success.
Another prior art guidable catheter mechanism includes a flexible catheter body tube which is formed to be as rigid in torsion as possible, while being longitudinally flexible, so that the entire body of the catheter may be twisted from side to side even though it be in a circuitous or tortuous path, and without a tendency to whiplash, that is to resist turning until a certain torque is applied at which time the entire rotation applied to the proximal end is unleashed. One such system is described in my U.S. Pat. No. 3,503,385.
In this earlier patent named above, forward guidance is provided by forming the distal end of the catheter with a flexible, resilient curve and by providing a stainless steel control wire within the lumen during insertion. The control wire is held by a control mechanism or manipulator which permits it to be moved axially of the catheter, forwardly into the curve, to within a fraction of an inch of the distal end and rearedly from the curve. When the control wire is in its forward most position, extending past the curve, it causes the curve in the catheter to substantially straighten so that the catheter may be directed forwardly during insertion. When the wire was withdrawn from the catheter tip, its curved shape is resumed and the catheter may be caused to enter a branching vessel. Thus, the wire is often referred to as a "deflector" wire.
The tip of my earlier guidable catheter assembly was formed with a double curvature including a distal curve which functions as desired above, and a few inches proximal thereof a secondary curve, which facilitates the leading of the catheter by riding against the wall opposite the cannulated orifice.
The catheter manipulator consists of a manually operated assembly to which the proximal end of the catheter is connected to communicate with a fluid supply channel formed in the forward portion of the device. This portion preferably included a swivel joint by which the forward end may be rotated independently of the rearward portion to rotate the catheter during insertion.
The rearward portion of the fluid supply channel communicates with one or more fluid inlet fittings, and terminates in a fluid-tight gland through which the control wire passes.
To the rearward of the fluid supply channel is a slide mechanism controlling the fore and aft motion of the stainless steel control wire. This consisted of a slidable member to which the end of the control wire is loosely attached and which is free to slide back and forth axially of the fluid supply channel.
The manipulator is thus provided not only for control of the catheter, both by rotation and fore and aft motion of the control wire, but also for the introduction of appropriate fluids both during the time that the catheter is being inserted and afterwards when an injection is to be made. In addition, the manipulator is designed to be easily disassembled for cleaning.
However, a problem arose in my earlier design causing the control wire to bind within the lumen when the catheter was inserted into a blood vessel. Obviously, the binding of the control wire within the catheter significantly impairs the physician's ability to properly guide the catheter along its entire course of travel. Binding occurred with axial wire movement. The double curvature of my prior art catheter exacerbated the binding problem.